The blockage of human arteries can lead to a variety of serious medical complications. Arterial blockages reduce blood flow through the affected artery and may result in damage to the tissue that is relying upon the blood's supply of oxygen (ischemia). For example, if the blockage is in an artery that supplies blood to the heart itself, a heart attack may result.
Thrombosis and atherosclerosis are common ailments that result from the deposition of thrombus on the walls of blood vessels. When such deposits harden, they are commonly referred to as plaque. These plaque deposits occur commonly in blood vessels that feed the brain, heart, and limbs of the human body. Stasis, incompetent valves, and trauma in the venous circulation are common causes of thrombosis, which can often manifest as a deep vein thrombosis in the peripheral vasculature. When such deposits build-up in localized regions of the blood vessel, they can restrict blood flow and cause a serious health risk.
In addition to forming in the natural vasculature, thrombosis is a serious problem in “artificial” blood vessels, particularly in peripheral femoral-popliteal and coronary bypass grafts and dialysis access grafts and fistulas. The creation of such artificial blood vessels requires anastomotic attachment at one or more locations in the vasculature. Such sites are particularly susceptible to thrombus formation due to narrowing caused by intimal hyperplasia, and thrombus formation at these sites is a frequent cause of failure of the implanted graft or fistula. The arterio-venous grafts and fistulas that are used for dialysis access are significantly compromised by thrombosis at the sites of anastomotic attachment and elsewhere. Thrombosis often occurs to such an extent that the graft needs to be replaced within a few years or even a few months.
A variety of methods have been developed for treating thrombosis and atherosclerosis in the coronary and peripheral vasculature as well as in implanted grafts and fistulas. Such techniques include pharmacologic thrombolytic therapy, given either intravenously or intra-arterially (Hacke W. et al., JAMA, 274:1017-1025, 1995; del Zoppo G. J. et al., Stroke, 29:4-11, 1998), surgical procedures, such as coronary artery bypass grafting, and minimally invasive procedures, such as angioplasty atherectomy, transmyocardial and revascularization. In particular, a variety of techniques generally referred to as “thrombectomy” have been developed. Thrombectomy generally refers to procedures for the removal of relatively soft thrombus and clot from vasculature. Removal is usually achieved by mechanically disrupting the clot, and can optionally include the administration of thrombolytic agents. The disrupted thrombus or clot is then withdrawn through a catheter, typically with a vacuum or mechanical transport device.
Thrombectomy generally differs from angioplasty and atherectomy in the type of occlusive material that is being treated and in the level of care taken to avoid damage to the blood vessel wall. The material removed in most thrombectomy procedures is relatively soft, such as the clot formed in deep vein thrombosis, and is usually not hardened plaque of the type treated by angioplasty in the coronary vasculature. Moreover, it is usually an objective of thrombectomy procedures to have minimum or no deleterious interaction with the blood vessel wall. Ideally, the clot will be disrupted and pulled away from the blood vessel wall with no harmful effect on the wall itself.
While successful thrombectomy procedures have been achieved, most have required compromise between the competing objectives of removing the thrombosis and minimizing injury to the blood vessel wall. While more aggressive thrombectomy procedures employ rotating blades that can be very effective at thrombus removal, they present a significant risk of injury to the blood vessel wall. Alternatively, those procedures that rely primarily on vacuum extraction together with minimum disruption of the thrombus, often fail to achieve sufficient thrombus removal.
U.S. Pat. No. 5,904,698 describes a catheter having an expandable mesh with a blade or electrode for shearing obstructive material, which penetrates the mesh when the mesh is expanded in a blood vessel. Other catheters having expandable meshes, cages, and/or shearing elements are described in U.S. Pat. Nos. 5,972,019; 5,954,737; 5,795,322; 5,766,191; 5,556,408; 5,501,408; 5,330,484; 5,116,352; and 5,410,093; and WO 96/01591. Catheters with helical blades and/or Archimedes screws for disrupting and/or transporting clot and thrombus are described in U.S. Pat. Nos. 5,947,985; 5,695,501; 5,681,335; 5,569,277; 5,569,275; 5,334,211; and 5,226,909. Other catheters of interest for performing thrombectomy and other procedures are described in U.S. Pat. Nos. 5,928,186; 5,695,507; 5,423,799; 5,419,774; 4,762,130; 4,646,736; and 4,621,636. Techniques for performing thrombectomy are described in Sharafudin et al. (JVIR 8:911-921, 1997) and Schmitz-Rode et al. (Radiology 180:135-137, 1991).
One of the problems with many of these devices, however, is that particulate matter (e.g., thrombus, atheroma, or other embolic or occlusive material) may be released from the wall of the vessel during the procedure. If such particulate matter travels downstream, it may become lodged or otherwise harm the patient. For example, ischemic stroke may occur when such emboli are released in the carotid or cerebral arteries and travel to the patient's brain. To prevent or minimize damage from emboli, vascular filters have been suggested that are typically disposed on a device such as a catheter, guidewire, or sheath. These devices may be introduced within a blood vessel downstream of a location being treated, and the filter on the device deployed across the vessel to capture embolic material released during the procedure. Upon completion of the procedure, the filter may be collapsed, trapping emboli therein, and then the device may be removed from the patient. Catheters having expandable filters at their distal ends are described in U.S. Pat. No. 4,928,858 and PCT publications WO99/44542 and WO99.44510.
The United States Food and Drug Administration (FDA) has approved a total of eight mechanical thrombectomy devices (MTDs) for use in thrombosed hemodialysis grafts (Kasirajan K. et al., J. Vasc. Interv. Radiol., 2001, 12:405-411). Generally, the approved MTDs can be classified into two categories: (i) mechanical lysis only (non-aspirating) devices and (ii) mechanical and aspirating devices. The AMPLATZ thrombectomy device (CLOT BUSTER; MICROVENA, White Bear Lake, Minn.), ARROW-TREROTOLA PTD (ARROW INTERNATIONAL, Reading, Pa.), and CASTANEDA OVER-THE-WIRE BRUSH (MICRO THERAPEUTICS, Aliso Viego, Calif.) are categorized mechanical non-aspirating devices and ANGIOJET (POSSIS MEDICAL; Minneapolis Minn.), GELBFISH-ENDOVAC (BOSTON SCIENTIFIC/MEDI-TECH, Brooklyn, N.Y.), HYDROLYSER (CORDIS, Miami, Fla.), OASIS (BOSTON SCIENTIFIC/MEDI-TECH, Watertown, Mass.) are categorized under mechanical aspirating devices. The ANGIOJET LF140 (POSSIS MEDICAL, Minneapolis, Minn.) is the only FDA approved device for use in peripheral arterial occlusive disease. These devices are currently being used or undergoing clinical evaluation for the treatment of acute and chronic limb-threatening ischemia.
Stroke is characterized by a sudden loss of blood supply to the brain, which results in loss of neurological function. Stroke is the third leading cause of death in the United States (150,000 cases per year) and the leading cause of adult disability (“2002 Heart and Stroke Statistical Update”, American Heart Association, Dallas, Tex., 2001). Approximately 700,000 strokes occur annually in the U.S., accounting for costs of over $26 billion/year for treatment and rehabilitation. Stroke is currently classified into two categories: hemorrhagic and ischemic. Ischemic stroke is the most common type and accounts for 85% of all stroke cases. Ischemic stroke (i.e., thromboembolic stroke) occurs when arteries supplying blood to the brain are occluded by thrombus or other embolic material (e.g., calcifications, cholesterol, plaque, etc.).
Current treatment modalities include pharmacologic thrombolytic therapy; however, all thrombolytic drugs are not indicated for all stroke victims and are not effective for all thromboembolic occlusions. The treatment of ischemic stroke patients with tissue plasminogen activator (tPA) is currently the only FDA approved treatment in the United States. However, tPA has been shown to benefit patients only if administered within a 3 hour time window after the onset of neurological symptoms. Therefore, a poor success rate in treatment of stroke is observed. Moreover, the use of tPA is associated with a high risk of hemorrhage and cannot be given to all patients. Endovascular mechanical thrombolytic devices could be used to treat ischemic stroke patients less invasively and more effectively. Unfortunately, there currently exists no FDA approved device for ischemic stroke treatment. Mechanical thrombectomy devices may increase the risk of arterial performation, dissection, or endothelial injury, which can result in intracranial hemorrhage and worsening of neurological deficits, for example. Therefore, making such devices that will eliminate or even reduce these risks is an extremely challenging task. For example, a device adapted to treat ischemic stroke should be miniaturized to fit inside intracranial arteries, which are relatively small (1 mm to 3.5 mm in diameter). Intracranial arteries are fragile and tortuous; therefore, the device should also be highly flexible and maneuverable. The use of such devices, along with tPA, may benefit patients by providing a quick recovery from ischemic stroke.
Preliminary studies on the safety, efficacy, and device limitations have spurred an interest in percutaneous techniques for thrombus debulking as stand-alone therapy or as an adjunct to pharmacologic thrombolysis. The devices have various mechanisms or combinations of mechanisms to optimize thrombus removal. Efficacy of thrombus removal is balanced by the propensity for vessel wall damage and distal embolization, especially for vessel wall-contact devices.
Therefore, there is a need for a device that is simple in design and is highly maneuverable to permit navigation through various lumen systems of the body, such as the intracranial, urinary, biliary, bronchial, and coronary systems, thereby facilitating effective disruption and removal of occlusive material while minimizing the risk of injury to the lumen wall.